public class 有参无返 {
    public static void triangle(int a ,int b){
        double area=a*b*0.5;
        System.out.println("该三角形面积为"+area);
    }
    public static void square(int a ,int b){
        double area=a*b;
        System.out.println("该正方形面积为"+area);
    }
    public static void rectangle(int a ,int b){
        double area=a*b;
        System.out.println("该长方形面积为"+area);
    }


    public static void main(String[] args) {
        triangle(4,5);
    }
}
